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United States Patent |
5,700,780
|
Beaulieu
,   et al.
|
December 23, 1997
|
Antiviral peptide derivatives having a 2-oxoalkyl amino acid side chain
Abstract
Disclosed herein are peptide derivatives of the formula X›--NR.sup.1
--CH(R.sup.2)--C(W.sup.1)!.sub.n --NH--CR.sup.3
(R.sup.4)--C(W.sup.2)--NR.sup.5 --CH›CH.sub.2
C(O)--Y!--C(W.sup.3)--NH--CR.sup.6 --›CR.sup.7
--(R.sup.8)--COOH!--C(W.sup.4)--NH--CR.sup.9 (R.sup.10)--Z wherein X is a
terminal group, for example, alkanoyl or phenylalkanoyl radicals, R.sup.1
is hydrogen, alkyl or phenylalkyl, R.sup.2, R.sup.4 and R.sup.10 am
selected from amino acid or derived amino acid residues, R.sup.3, R.sup.5,
R.sup.6, R.sup.7, R.sup.8 and R.sup.9 are hydrogen or alkyl, or R.sup.7
and R.sup.8 are joined to form a cycloalkyl, W.sup.1, W.sup.2, W.sup.3 and
W.sup.4 are oxo or thioxo, Y is, for example, an alkyl or a cycloalkyl, Z
is a terminal group, for example, COOH or CH.sub.2 OH, and n is 0 or 1.
The derivatives are useful for treating herpes infections.
Inventors:
|
Beaulieu; Pierre Louis (Montreal, CA);
Deziel; Robert (Mont-Royal, CA);
Lavallee; Pierre (Rosemere, CA)
|
Assignee:
|
Boehringer Ingelheim (Canada), Ltd. (Laval, CA)
|
Appl. No.:
|
540862 |
Filed:
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October 11, 1995 |
Foreign Application Priority Data
Current U.S. Class: |
514/17; 514/18; 530/329; 530/330; 530/331 |
Intern'l Class: |
A61K 038/00; C07K 005/00 |
Field of Search: |
514/17,18
530/329,330,331
|
References Cited
U.S. Patent Documents
4795740 | Jan., 1989 | Cohen et al. | 514/14.
|
4814432 | Mar., 1989 | Freidinger et al. | 530/329.
|
4837304 | Jun., 1989 | Garsky et al. | 530/328.
|
4845195 | Jul., 1989 | Colonno et al. | 530/330.
|
5502036 | Mar., 1996 | Adams et al. | 514/17.
|
Foreign Patent Documents |
0352000 | Jan., 1990 | EP.
| |
0357332 | Mar., 1990 | EP.
| |
0374097 | Jun., 1990 | EP.
| |
Other References
Gaudreau et al., J. Biol. Chem. vol. 262, No. 26, pp. 12413-12416, Sep.
1987.
|
Primary Examiner: Tsang; Cecilia J.
Assistant Examiner: Celsa; Bennett
Attorney, Agent or Firm: Raymond; R. P., Devlin; M-E. M., Stempel; A. R.
Parent Case Text
This is a continuation of application Ser. No. 08/090,682, filed Jul. 13,
1993 (abandoned), which is a continuation of application Ser. No.
07/926,605, filed Aug. 7, 1992 (abandoned), which is a continuation of
application Ser. No. 07/547,712, filed Jul. 3, 1990 (abandoned).
Claims
The embodiments of this invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A peptide of formula I
##STR2##
wherein X is 2-ethylbutanoyl or phenylpropionyl
R.sup.1 is methyl
R.sup.2 is 1-methylethyl
R.sup.3 is hydrogen
R.sup.4 is 1-methylpropyl or 1,1-dimethylethyl
R.sup.5 is hydrogen
R.sup.6 is hydrogen
R.sup.7 and R.sup.8, each independently, are hydrogen or methyl
R.sup.9 is hydrogen
R.sup.10 is 2-methylpropyl or 2,2-dimethylpropyl
W.sup.1, W.sup.2, W.sup.3 and W.sup.4 are oxo
Y is methyl, pentyl, heptyl, undecyl or cyclopentyl
Z is hydrogen, COOH or COHN.sub.2
and n is the integer zero or one
or a therapeutically acceptable salt thereof.
2. The peptide of claim 1 selected from the group of:
PhCH.sub.2 CH.sub.2 CO-N-Me-Val-Ile-NHCH(2-oxononyl)-CO-Asp-Leu-OH
PhCH.sub.2 CH.sub.2
CO-N-Me-Val-Ile-NHCH(2-cyclopentyl-2-oxoethyl)-CO-Asp-Leu-OH
PhCH.sub.2 CH.sub.2 CO-N-Me-Val-Ile-NHCH(2-oxotridecyl)-CO-Asp-Leu-NH.sub.2
2-Ethylbutanoyl-Ile-NHCH(2-oxotridecyl)-CO-Asp-Leu-OH
PhCH.sub.2 CH.sub.2 CO-N-Me-Val-Ile-NHCH(2-oxopropyl)-CO-Asp-Leu-OH
2-Ethylbutanoyl-Ile-NHCH(2-oxononyl)-CO-Asp-Leu-OH
2-Ethylbutanoyl-Tbg-NHCH(2-oxoheptyl)-CO-Asp-Leu-OH
2-Ethylbutanoyl-Tbg-NHCH(2-oxononyl)-CO-Asp-Leu-OH
2-Ethylbutanoyl-Tbg-NHCH(2-oxononyl)-CO-NHCH{C(CH.sub.3).sub.2
COOH}-CO-Leu-OH or
2-Ethylbutanoyl-Tbg-NHCH(2-cyclopentyl-2-oxoethyl)-CO-Asp-NHCH.sub.2
CH.sub.2 C(CH.sub.3).sub.3.
3. A pharmaceutical composition comprising a peptide as recited in claim 1,
or a therapeutically acceptable salt thereof, and a pharmceutically or
veterinarily acceptable carrier.
4. A cosmetic composition comprising a peptide as recited in claim 1, or a
therapeutically acceptable salt thereof, and a physiologically acceptable
carrier suitable for topical application.
5. A method of treating a herpes viral infection in a mammal comprising
administering thereto an effective amount of a peptide as recited in claim
1, or a therapeutically acceptable salt thereof.
6. A method of claim 5 wherein the herpes viral infection is a herpes
simplex viral infection.
Description
FIELD OF THE INVENTION
This invention relates to peptide derivatives having antiviral properties
and to means for using the derivatives to treat viral infections. More
specifically, the invention relates to peptide derivatives (hereinafter
called "peptides") exhibiting activity against herpes viruses, to
pharmaceutical compositions comprising the peptides, and to a method of
using the peptides to treat herpes infections.
BACKGROUND OF THE INVENTION
The family of herpes viruses is responsible for a wide range of infections
that afflict humans and many important domestic animals. The diseases
caused by these viruses range from bothersome cold sores to highly
destructive infections of the central nervous system (encephalitis). The
more common members of this family include herpes simplex virus (types 1
and 2) responsible for cold sores and genital lesions; varicella zoster
virus which causes chicken pox and shingles; and Epstein-Barr virus which
causes infectious mononucleosis. Although some significant advances have
been made in the last decade in antiviral therapy, the need for effective,
safe therapeutic agents for treating herpes viral infections continues to
exist. For a recent review of current therapeutic agents in this area, see
M. C. Nahata, "Antiviral Drugs: Pharmacokinetics, Adverse Effects and
Therapeutic Use", J. Pharm. Technol., 3, 100 (1987).
The present application discloses a group of peptide derivatives having
activity against herpes viruses. The relatively selective action of these
peptides against herpes viruses, combined with a wide margin of safety,
renders the peptides as desirable agents for combating herpes infections.
The association of peptides with anti-herpes activity is uncommon.
Instances of reports of such an association include B. M. Dutia et al.,
Nature, 321, 439 (1986), E. A. Cohen et al., Nature, 321, 441 (1986), J.
H. Subak-Sharpe et al., UK patent application 2185024, published Jul. 8,
1987, E. A. Cohen et al., European patent application 246630, published
Nov. 25, 1987, R. Freidinger et al., European patent application 292255,
published Nov. 23, 1988, and R. Freidinger et al., U.S. Pat. No.
4,814,432, issued Mar. 21, 1989. The subject peptides of the previous
reports can be distinguished from the peptides of the present application
by characteristic structural and biological differences.
SUMMARY OF THE INVENTION
The peptides of this invention are represented by formula 1
X›--NR.sup.1 --CH(R.sup.2)--C(W.sup.1)!.sub.n --NH--CR.sub.3
(R.sub.4)--C(W.sub.2)--NR--CH›CH.sub.2 C(O)--Y!--C(W.sup.3)--NH--CR.sup.6
--›CR.sup.7 (R.sup.8)--COOH!--C(W.sup.4)--NH--CR.sup.9 (R.sup.10)--Z1
wherein X is (1-10C)alkanoyl, (1-10C)alkoxycarbonyl, benzoyl, benzoyl
monosubstituted or disubstituted with a substituent selected from halo,
hydroxy, lower alkyl, lower alkoxy, phenyl, 2-carboxyphenyl or benzyl,
2,2-diphenylacetyl, phenyl(1-10C)alkanoyl or phenyl(1-10C)alkanoyl
monosubstituted or disubstituted on the aromatic portion thereof with a
substituent selected from halo, hydroxy, lower alkyl, lower alkoxy or
phenyl;
R.sup.1 is hydrogen, lower alkyl or phenyl(lower)alkyl;
R.sup.2 is lower alkyl, hydroxy(lower)alkyl or mercapto(lower alkyl);
R.sup.3, R.sup.5, R.sup.6 and R.sup.9 each independently is hydrogen or
lower alkyl;
R.sup.4 is hydrogen, lower alkyl, hydroxy(lower)alkyl,
mercapto(lower)alkyl, methoxy(lower)alkyl, methylthio(lower)alkyl lower
cycloalkyl or (lower cycloalky)methyl;
R.sup.7 and R.sup.8 each independently is hydrogen or lower alkyl, or
R.sup.7 and
R.sup.8 together with the carbon atom to which they are attached form a
lower cycloalkyl;
R.sup.10 is lower alkyl, lower alkenyl or (lower cycloalkyl)methyl;
W.sup.1, W.sup.2, W.sup.3 and W.sup.4 each independently is oxo or thioxo;
Y is (1-14C)alkyl, lower cycloalkyl, lower alkyl monosubstituted with a
lower cycloalkyl, phenyl(lower)alkyl, phenyl(lower)alkyl wherein the
aromatic portion thereof is substituted with halo, lower alkyl or lower
alkoxy, or (Het)-lower alkyl wherein Het represents a five or six membered
heterocyclic radical containing one or two heteroatoms selected from
nitrogen, oxygen or sulfur,
Z is hydrogen, COOH, CH.sub.2 COOH, 5-1H-tetrazolyl, COOR.sup.11 wherein
R.sup.11 is lower alkyl, CH.sub.2 OH, CONR.sup.12 R.sup.13 wherein R.sup.12
and R.sup.13 each independently is hydrogen or lower alkyl, or
CON(R.sup.14)OH wherein
R.sup.14 is hydrogen or lower alkyl; and
n is the integer zero or one;
or a therapeutically acceptable salt thereof.
A preferred group of the peptides of this invention is represented by
formula 1 wherein X is (1-10C)alkanoyl, (1-10C)alkoxycarbonyl, benzoyl,
benzoyl monosubstituted with halo, hydroxy, lower alkyl, lower alkoxy,
phenyl, 2-carboxyphenyl or benzyl, 2,2-diphenylacetyl,
phenyl(1-10C)alkanoyl or phenyl(1-10C)alkanoyl monosubstituted or
disubstituted on the aromatic portion thereof with a substituent selected
from halo, hydroxy, lower alkyl, lower alkoxy or phenyl; R.sup.1 to
R.sup.10, inclusive, and W.sup.1 to W.sup.4, inclusive, are as defined
hereinabove; Y is (1-14C)alkyl, lower cycloalkyl, lower cycloalkylmethyl,
phenyl(lower)alkyl or (Het)-lower alkyl wherein Het is a heterocyclic
radical selected from 2-pyrrolyl, 2-pyridinyl, 4-pyridinyl, 2-furyl,
2-isoxazolyl and 2-thiazolyl; Z is as defined hereinabove; and n is the
interger zero or one; or a therapeutically acceptable salt thereof.
A more preferred group of the peptides is represented by formula 1 wherein
X, R.sup.7, R.sup.8 and R.sup.10 are as defined hereinabove; R.sup.1 is
lower alkyl; R.sup.2 is lower alkyl or hydroxy(lower)alkyl; R.sup.3,
R.sup.5, R.sup.6 and R.sup.9 each independently is hydrogen or methyl;
R.sup.4 is hydrogen, lower alkyl, hydroxy(lower)alkyl,
methoxy(lower)alkyl, lower cycloalkyl or (lower cycloalkyl)methyl;
W.sup.1, W.sup.2, W.sup.3 and W.sup.4 are oxo; Y is (1-14C)alkyl, lower
cycloalkyl, lower cycloalkylmethyl, phenyl(lower)alkyl or pyridinyl(lower
alkyl); Z is hydrogen, COOH, CH.sub.2 COOH, 5-1H-tetrazolyl, CH.sub.2 OH,
CONR.sup.12 R.sup.13 wherein R.sup.12 and R.sup.13 each independently is
hydrogen or lower alkyl, or CON(R.sup.14)OH wherein R.sup.14 is hydrogen
or lower alkyl; and n is the integer zero or one; or a therapeutically
acceptable salt thereof.
A most preferred group of the peptides is represented by formula 1 wherein
X is acetyl, 2-ethylbutanoyl, 4-methylpentanoyl, octanoyl, Boc, benzoyl,
2-biphenylylcarbonyl, 2-(2'-carboxy)biphenylylcarbonyl, phenylacetyl,
phenylpropionyl, (4-hydroxyphenyl)propionyl or
(3,4-dihydroxyphenyl)propionyl; R.sup.1 is methyl; R.sup.2 is
1-methylethyl, 1,1-dimethylethyl, 1-methylpropyl or 1-hydroxyethyl;
R.sup.5 is hydrogen or methyl; R.sup.4 is hydrogen, lower alkyl,
hydroxymethyl, 1-hydroxyethyl, 1-methoxyethyl, cyclopentyl or
cyclohexylmethyl; R.sup.5 is hydrogen or methyl; R.sup.6 is hydrogen;
R.sup.7 and R.sup.8 each independently is hydrogen, methyl, ethyl or
propyl, or R.sup.7 and R.sup.8 together with the carbon atom to which they
are joined form a lower cycloalkyl; R.sup.9 is hydrogen or methyl;
R.sup.10 is 2-methylpropyl, 3-methylbutyl or 2,2-dimethylpropyl; W.sup.1,
W.sup.2, W.sup.3 and W.sup.4 are oxo; Y is methyl, hexyl, heptyl,
1-methylheptyl, decyl, undecyl, cyclopentyl, cyclohexyl, cyclohexylmethyl
or phenylpropylethyl; Z is hydrogen, COOH, CH.sub.2 COOH, 5-1H-tetrazolyl,
CH.sub.2 OH, CONR.sup.12 R.sup.13 wherein R.sup.12 and R.sup.13 each
independently is hydrogen, methyl, ethyl or propyl, or CON(R.sup.14)OH
wherein R.sup.14 is hydrogen or methyl; and n is the integer one; or a
therapeutically acceptable salt thereof.
Included within the scope of this invention is a pharmaceutical composition
comprising an anti-herpes virally effective amount of a peptide of formula
1, or a therapeutically acceptable salt thereof, and a pharmaceutically or
veterinarily acceptable carrier.
Also included within the scope of this invention is a cosmetic composition
comprising a peptide of formula 1, or a therapeutically acceptable salt
thereof, and a physiologically acceptable carrier suitable for topical
application.
An important aspect of the invention involves a method of treating a herpes
viral infection in a mammal by administering to the mammal an anti-herpes
virally effective amount of the peptide of formula 1, of a therapeutically
acceptable salt thereof.
Another important aspect involves a method of inhibiting the replication of
herpes virus by contacting the virus with a herpes viral ribonucleotide
reductase inhibiting amount of the peptide of formula 1, or a
therapeutically acceptable salt thereof.
Processes for preparing the peptides of formula 1 are described
hereinafter.
DETAILS OF THE INVENTION
General
Alternatively, formula 1 can be illustrated as follows:
##STR1##
The term `residue` with reference to an amino acid or amino acid derivative
means a radical derived from the corresponding .alpha.-amino acid by
eliminating the hydroxyl of the carboxy group and one hydrogen of the
.alpha.-amino group.
In general, the abbreviations used herein for designating the amino acids
and the protective groups are based on recommendations of the IUPAC-IUB
Commision of Biochemical Nomenclature, see European Journal of
Biochemistry 138, 9 (1984). For instance, Gly, Val, Thr, Ala, Ile, Asp,
Ser and Leu represent the residues of glycine, L-valine, L-threonine,
L-alanine, L-isoleucine, L-aspartic acid L-serine and L-leucine,
respectively.
The asymmetric carbon atoms residing in the principal linear axis (i.e. the
backbone) of the peptides of formula 1, exclusive of the terminal groups,
have an S configuration. Asymmetric carbon atoms residing in the side
chain of an amino acid or derived amino acid residue, including those in
terminal groups, may also have the R configuration. Furthermore, with
respect to disubstituted benzoyl and disubstituted phenyl(1-10C)alkanoyl
as defined for X of peptides of formula 1, the substituents are selected
on, the basis that they do not interfere with each others presence.
The term `halo` as used herein means a halo radical selected from bromo,
chloro, fluoro or iodo.
The term "lower alkyl" as used herein, either alone or in combination with
a radical, means straight chain alkyl radicals containing one to six
carbon atoms and branched chain alkyl radicals containing three to six
carbon atoms and includes methyl, ethyl, propyl, butyl, hexyl,
1-methylethyl, 1-methylpropyl, 2-methylpropyl and 1,1-dimethylethyl.
The term "lower alkenyl" as used herein means straight chain alkenyl
radicals containing two to six carbon atoms and branched chain alkenyl
radicals containing three to six carbon atoms and includes vinyl,
1-propenyl, 1-methylethenyl, 2-methyl-1-propenyl, 2-methyl-2-propenyl and
2-butenyl.
The term "lower cycloalkyl" as used herein, either alone or in combination
with a radical, means saturated cyclic hydrocarbon radicals containing
from three to six carbon atoms and includes cyclopropyl, cyclobutyl,
cyclopentyl and cyclohexyl.
The term "lower alkoxy" as used herein means straight chain alkoxy radicals
containing one to four carbon atoms and branched chain alkoxy radicals
containing three to four carbon atoms and includes methoxy, ethoxy,
propoxy, 1-methylethoxy, butoxy and 1,1-dimethylethoxy. The latter radical
is known commonly as tertiary-butyloxy.
The term "(1-14C)alkyl" as used herein means straight and branched chain
alkyl radicals containing from one to fourteen carbon atoms. The term
"(1-10C)alkoxycarbonyl" as used herein, means straight and branched chain
alkoxycarbonyl radicals containing from one to ten carbon atoms in their
alkoxy portion and includes, for example, ethoxycarbonyl,
tertiary-butyloxycarbonyl and octyloxycarbonyl. The term "(1-10C)alkanoyl"
as used herein means straight and branch chain 1-oxoalkyls containing from
one to ten carbon atoms and includes, for example, acetyl,
4-methylpentanoyl and octanoyl. The term "phenyl(1-10)alkanoyl as used
herein means phenyl substituted 1-oxoalkyl radicals wherein the 1-oxoalkyl
portion thereof is a straight or branched chain 1-oxoalkyl containing from
one to ten carbon atoms; for example, 1-oxo-3-phenylpropyl and
1-oxo-5-methyl-6-phenylhexyl.
The symbol ".PSI.›CSNH!" used between the three-letter representations of
two amino acid residues means that the normal amide bond between those
residues in the peptide, being represented, has been replaced with a
thioamide bond.
Additional abbreviations or symbols used hereafter are:
______________________________________
Boc 1,1-methylethoxycarbonyl or
tertiary-butyloxycarbonyl
DAT desaminotyrosyl or 1-oxo-3-(4-
hydroxyphenyl)phenylpropyl
Ph phenyl
PhCH.sub.2 CH--CO
1-oxo-3-phenylpropyl
N--Me--Val N-methylvalyl residue
Tbg tertiary-butylglycine or 2(S)-
amino-3,3-dimethylbutanoic acid
residue
Asp(cyBu) (S)-.alpha.-amino-1-carboxycyclo-
butaneacetic acid residue
Asp(cyPn) (S)-.alpha.-amino-1-carboxycyclo-
pentaneacetic acid residue
______________________________________
The term "pharmaceutically acceptable carrier" or "veterinarily acceptable
carrier" as use herein means a non-toxic, generally inert vehicle for the
active ingredient which does not adversely affect the ingredient.
The term "physiologically acceptable carrier" as used herein means an
acceptable cosmetic vehicle of one or more non-toxic excipients which do
not react with or reduce the effectiveness of the active ingredient
contained therein.
The term "veterinarily acceptable carrier" as used herein means a
physiologically acceptable vehicle for administering drug substances to
domestic animals comprising one or more non-toxic pharmaceutically
acceptable excipients which do not react with the drug substance or reduce
its effectiveness.
The term "effective amount" means a predetermined antiviral amount of the
antiviral agent, i.e. an amount of the agent sufficient to be effective
against the viral organisms in vivo.
The term "coupling agent" as used herein means an agent capable of
effecting the dehydrative coupling of an amino acid or peptide free
carboxy group with a free amino group of another amino acid or peptide to
form an amide bond between the reactants. Similarly, such agents can
effect the coupling of an acid and an alcohol to form corresponding
esters. The agents promote or facilitate the dehydrative coupling by
activating the carboxy group. Descriptions of such coupling agents and
activated groups are included in general text books of, peptide chemistry;
for instance, E. Schroder and K. L. Lubke, "The Peptides", Vol. 1,
Academic Press, New York, N.Y., 1965, pp 2-128, and K. D. Kopple,
"Peptides and Amino acids", W. A. Benjamin, Inc., New York, N.Y., 1966, pp
33-51. Examples of coupling agents are thionyl chloride,
diphenylphosphoryl azide, 1,1'-carbonyldiimidazole,
dicyclohexylcarbodiimide, N-hydroxysuccinimide, or 1-hydroxybenzotriazole
in the presence of dicyclohexylcarbodiimide. A very practical and useful
coupling agent is (benzotriazol-1-yloxy)tris(dimethylamino)-phosphonium
hexafluorophosphate, described by B. Castro et al., Tetrahedron Letters,
1219 (1975), see also D. Hudson, J. Org. Chem., 53, 617 (1988), either by
itself or in the presence of 1-hydroxybenzotriazole.
Process
The peptides of formula 1 can be prepared by processes which incorporate
therein methods commonly used in peptide synthesis such as classical
solution coupling of amino acid residues and/or peptide fragments, and if
desired solid phase techniques. Such methods are described, for example,
by E. Schroder and K. Lubke, cited above, in the textbook series, "The
Peptides: Analysis, Synthesis, Biology", E. Gross et at., Eds., Academic
Press, New York, N.Y., 1979-1987, Volumes 1 to 8, and by J. M. Stewart and
J. D. Young in "Solid Phase Peptide Synthesis", 2nd ed., Pierce Chem. Co.,
Rockford, Ill., USA, 1984.
A common feature of the aforementioned processes for the peptides is the
protection of the reactive side chain groups of the various amino acid
residues or derived amino acid residues with suitable protective groups
which will prevent a chemical reaction from occurring at that site until
the protective group is ultimately removed. Usually also common is the
protection of an .alpha.-amino group on an amino acid or a fragment while
that entity reacts at the carboxy group, followed by the, selective
removal of the .alpha.-amino protective group to allow subsequent reaction
to take place at that location. Usually another common feature is the
initial protection of the C-terminal carboxyl of the amino acid residue or
peptide fragment, if present, which is to become the C-terminal function
of the peptide, with a suitable protective group which will prevent a
chemical reaction from occurring at that site until the protective group
is removed after the desired sequence of the peptide has been assembled.
In general, therefore, a peptide of formula 1 can be prepared by the
stepwise coupling in the order of the sequence of the peptide of the amino
acid or derived amino acid residues, or fragments of the peptide, which if
required are suitably protected, and eliminating all protecting groups, if
present, at the completion of the stepwise coupling to obtain the peptide
of formula 1. More specific processes are illustrated in the examples
hereinafter.
The peptide of formula 1 of this invention can be obtained in the form of a
therapeutically acceptable salt.
In the instance where a particular peptide has a residue which functions as
a base, examples of such salts are those with organic acids, e.g. acetic,
lactic, succinic, benzoic, salicylic, methanesulfonic or p-toluenesulfonic
acid, as well as polymeric acids such as tannic acid or carboxymethyl
cellulose, and also salts with inorganic acids such as hydrohalic acids,
e.g. hydrochloric acid, or sulfuric acid, or phorphoric acid. If desired,
a particular acid addition salt is convened into another acid addition
salt, such as a non-toxic, pharmaceutically acceptable salt, by treatment
with the appropriate ion exchange resin in the manner described by R. A.
Boissonnas et al., Helv. Chim. Acta, 43, 1849 (1960).
In the instance where a particular peptide has one or more free carboxy
groups, examples of such salts are those with the sodium, potassium or
calcium cations, or with strong organic bases, for example, triethylamine
or N-methylmorpholine.
Antiherpes Activity
The antiviral activity of the peptides of formula 1 can be demonstrated by
biochemical, microbiological and biological procedures showing the
inhibitory effect of the compounds on the replication of herpes simplex
viruses, types 1 and 2 (HSV-1 and HSV-2), and other herpes viruses, for
example, varicella zoster virus (VZV), Epstein-Barr virus (EBV), equine
herpes virus (EHV) and cytomegalovirus.
Noteworthy is the fact that all of the aforementioned viruses are dependent
on their own ribonucleotide reductase to synthesize deoxyribonucleotides
for their replication. Although this fact may not be directly linked with
the antiviral activity found for the present peptides, the latter
compounds have been shown so far to have antiviral properties against all
viruses dependent on ribonucleotide reductase to synthesis DNA for their
replication.
In the examples hereinafter, the inhibitory effect on herpes ribonucleotide
reductase is noted for exemplary peptides of formula 1. Noteworthy, in the
connection with this specific inhibition of herpes ribonucleotide
reductase, is the relatively minimal effect or absence of such an effect
of the peptides on cellular ribonucleotide reductase activity required for
normal cell replication.
A method for demonstrating the inhibitory effect of the peptides of formula
1 on viral replication is the cell culture technique; see, for example, T.
Spector et al., Proc. Nail. Acad. Sci. USA, 82, 4254 (1985).
The therapeutic effect of the peptides can be demonstrated in laboratory
animals, for example, by using an assay based on genital herpes infection
in Swiss Webster mice, described by E. R. Kern, et al., Antiviral
Research, 3, 253 (1983).
When a peptide of this invention, or one of its therapeutically acceptable
salts, is employed as an antiviral agent, it is administered topically or
systemically to warm-blood animals, e.g. humans, pigs or horses, in a
vehicle comprising one or more pharmaceutically acceptable carriers, the
proportion of which is determined by the solubility and chemical nature of
the peptide, chosen route of administration and standard biological
practice. For topical administration, the peptide can be formulated in
pharmaceutically accepted vehicles containing 0.1 to 10 percent,
preferably 0.5 to 5 percent, of the active agent. Such formulations can be
in the form of a solution, cream or lotion.
For systemic administration, the peptide of formula 1 is administered by
either intravenous, subcutaneous or intramuscular injection, in
compositions with pharmaceutically acceptable vehicles or carriers. For
administration by injection, it is preferred to use the peptide in
solution in a sterile aqueous vehicle which may also contain other solutes
such as buffers or preservatives as well as sufficient quantities of
pharmaceutically acceptable salts or of glucose to make the solution
isotonic.
Suitable vehicles or carriers for the above noted formulations are
described in standard pharmaceutical texts, e.g. in "Remington's
Pharmaceutical Sciences", 16th ed, Mack Publishing Company, Easton, Pa.,
1980.
The dosage of the peptide will vary with the form of administration and the
particular active agent chosen. Furthermore, it will vary with the
particular host under treatment. Generally, treatment is initiated with
small increments until the optimum effect under the circumstances is
reached. In general, the peptide is most desirably administered at a
concentration level that will generally afford antivirally effective
results without causing any harmful or deleterious side effects.
With reference to topical application, the peptide is administered
cutaneously in a suitable topical formulation to the infected area of the
body e.g. the skin or part of the oral or genital cavity, in an mount
sufficient to cover the infected area. The treatment should be repeated,
for example, every four to six hours until lesions heal. Healing results
usually within 3 to 4 days. No contraindications have been observed.
With reference to systemic administration, the peptide of formula 1 is
administered at a dosage of 10 mcg to 1000 mcg per kilogram of body weight
per day, although the aforementioned variations will occur. However, a
dosage level that is in the range of from about 100 mcg to 500 mcg per
kilogram of body weight per day is most desirably employed in order to
achieve effective results.
Another aspect of this invention comprises a cosmetic composition
comprising a herpes viral prophylactic amount of the peptide of formula 1,
or a therapeutically acceptable salt thereof, together with a
physiologically acceptable cosmetic carrier. Additional components, for
example, skin softeners, may be included in the formulation. The cosmetic
formulation of this invention is used prophylactically to prevent the
outbreak of herpetic lesions of the skin. The formulation can be applied
nightly to susceptible areas of the skin. Generally, the cosmetic
composition contains less of the peptide than corresponding pharmaceutical
compositions for topical application. A preferred range of the amount of
the peptide in the cosmetic composition is 0.01 to 0.2 percent by weight.
Although the formulation disclosed hereinabove am effective and relatively
safe medications for treating herpes viral infections, the possible
concurrent administration of these formulations with other antiviral
medications or agents to obtain beneficial results is not excluded. Such
other antiviral medications or agents include acyclovir and antiviral
surface active agents or antiviral interferons such as those disclosed by
S. S. Asculai and F. Rapp in U.S. Pat. No. 4,507,281, Mar. 26, 1985.
The following examples illustrate further this invention. Solution
percentages or ratios express volume to volume relationship, unless stated
otherwise. Abbreviations used in the examples include Boc:
t-butyloxycarbonyl; BOP:
(benzotriazol-1-yloxy)tris(dimethylamino)-phosphonium hexafluorophosphate;
Bzl: benzyl; CH.sub.2 Cl.sub.2 : methylenedichloride; DAT: desaminotyrosyl
or 1-oxo-3-(4-hydroxyphenyl)propyl; DIPEA: diisopropylethylamine; DMF:
dimethyl formamide; Et.sub.2 O: diethyl ether;, EtOAc: ethyl acetate;
EtOH: ethanol; HOBt: 1-hydroxybenzotriazole; HPLC: high performance liquid
chromatography: MeOH: methanol; TFA: trifluoroacetic acid. Temperatures
are given in degrees centigrade.
EXAMPLE 1
Preparation of the Intermediate Boc-2(S)-Amino-4-oxo-undecanoic Acid
Boc-Asp-OBzl (500 mg, 1.55 mmol) was dissolved in acetonitrile (10 ml) and
N,N'-carbonyldiimidazole (277 mg, 1.71 mmol) was added to the solution.
After 30 min, p-nitrobenzylmagnesium malonate (860 mg, 1.71 mmol) was
added and the mixture was stirred at room temperature (20.degree.-220C.)
for 1.5 h. The acetonitrile was evaporated. The residue was dissolved in
EtOAc, washed with 1N aqueous HCl, water and then brine. The organic phase
was dried (MgSO.sub.4) and concentrated under reduced pressure. The
resulting residue was purified by chromatography (SiO.sub.2, eluent:
hexane-EtOAc) to give Boc-2(S)-amino-4-oxo-1,6-hexanedioic acid 1-benzyl
ester 6-(4-nitrophenyl)methyl ester (600 mg, 80%). The latter compound
(3.25 g, 6.5 mmol) was dissolved in DMF (40 ml). Cs.sub.2 CO.sub.3 (2.33
g, 7.14 mmol) and hexyl iodide (1.51 g, 7.14 mmol) were added to the
solution. The mixture was stirred at room temperature for 18 h. The
solvent was evaporated. The residue was dissolved in EtOAc. The solution
was washed with 1N aqueous HCl and H.sub.2 O, dried (MgSO.sub.4) and
evaporated. The residue was purified by chromatography (SiO.sub.2,
eluent=hexane-EtOAc) to give
Boc-2(S)-amino-4-oxo-5-›(4-nitrophenyl)methoxycarbonyl!undecanoic acid
benzyl ester (630 mg). A solution of the latter compound (630 mg) in MeOH
(25 ml) was shaken on a Parr apparatus under an atmosphere of H.sub.2 in
the present of 20% Pd(OH).sub.2 /C (70 mg) for 18 h. After filtration and
concentration of the reaction mixture, the resulting residue was dissolved
in EtOAc. The solution was stirred with 1N aqueous HCl for 10 min. The
organic phase was separated, washed with H.sub.2 O, dried (MgSO.sub.4) and
evaporated. The residue was purified by chromatography (SiO.sub.2, eluent:
hexane-EtOAc) to give the title compound (150 mg). NMR and MS of the
product were in agreement with the expected structure.
The coupling of title compound with appropriate units for the preparation
of peptides of formula 1 was achieved with DCC/HOBt as the coupling agent.
EXAMPLE 2
Preparation of the Intermediate
Boc-2(S)-Amino-5-cyclopentyl-4-oxocyclopentanoic Acid
Boc-2(S)-amino-4-oxo-1,6-hexanedioic acid 1-benzyl ester
6-(4-nitrophenyl)methyl ester (4.8 g, 9.6 mmol) was dissolved in DMF (100
ml). Na.sub.2 CO.sub.3 (4.07 g, 38.4 mmol) and 1,4-diiodobutane (3.59 g,
11.6 mmol) were added to the solution. The mixture was stirred 18 h at
room temperature and then heated at 50.degree. for 3 h. Evaporation of the
reaction mixture, extraction of the resulting residue with EtOAc, washing
of the extract with 1N aqueous HCl and water, drying (MgSO,) and
evaporation of the extract gave a crude product. The crude product was
purified by chromatography (SiO.sub.2, eluent: hexane-EtOAc) to give the
corresponding benzyl ester of the title compound (4.3 g). The benzyl ester
of the latter compound was subjected to hydrogenolysis ›5% Pd(OH.sub.2)/C
in MeOH, 18 h! and worked up (see example 1) to give the title compound
(140 mg). NMR and MS of the product were in agreement with the expected
structure.
The coupling of the tide compound with other appropriate units for the
preparation of peptides of formula 1 was achieved with BOP, see
hereinafter.
Analogous derived amino acid intermediates having a ketone in their side
chain were prepared in a similar manner as described for example 1 and 2
using the appropriate alkyl iodide.
EXAMPLE 3
Preparation of the Intermediate Boc-Asp(OBzl).PSI.›CSNH!Leu-OBzl
A stirred mixture of Boc-Asp(OBzl)Leu-OBzl (2.90 g, 5.51 mmol) and
Lawesson's reagent (1.12 g, 2.7 mmol), see "U. Pederson et al.,
Tetrahedron, 38, 3267 (1982), in toluene (30 ml) was heated at reflux for
2 h. Column chromatography with SiO.sub.2 (3.5.times.30 cm) and elution
with CH.sub.2 Cl.sub.2 gave the title compound (2.0 g), MS: 543
(M+H).sup.+, as a yellow oil (major fraction).
Analogous thioamides were prepared in the same manner and incorporated into
the appropriate peptides of formula 1 according to conventional solution
phase peptide synthesis.
EXAMPLE 4
Preparation of 3-Alkyl- or 3,3-Dialkyl-L-aspartic Acid Intermediates and
(S)-.alpha.-Amine-1-carboxycycloalkylacetic Acid Intermediates
These intermediates, for example, Boc-Asp(cyPn)(OBzl)-OH, were prepared
according the method of M. Bochenska and J. F. Biernat, Rocz. Chem., g
1195 (1976); see Chem. Abstr., 86, 43990r (1977). More specifically
exemplified, (.+-.)-Boc-Asp(cyPn)(OBzl)-OH was prepared as follows: To a
solution of 1-bromocyclopentane-carboxylic acid ethyl ester ›17.1 g, 77.3
mmol, described by D. N. Harpp et al., J. Org. Chem., 46, 3420 (1975)! and
freshly distilled ethyl isocyanoacetate (12.7 g, 122 mmol) in a mixture of
dimethylsulfoxide and Et.sub.2 O (1:1, 120 ml) was added sodium hydride
(4.5 g, 60% dispersion in mineral oil, 122 mmol) in small portions over 5
h. The resulting red slurry was stirred at room temperature for 16 h after
which time it was treated with a saturated aqueous solution of ammonium
chloride (5 ml). The mixture was diluted with water (500 ml). The
resulting mixture was extracted (2.times.) with ethyl acetate. The ethyl
acetate layers were combined and washed with water (2.times.) and then
with brine. Drying (MgSO.sub.4), filtering and concentration of the
extract afforded a dark red oil. This material was flash chromatographed
through a 5.times.25 cm column of silica gel ›eluent: ethyl acetate-hexane
(1:10)!. Concentration of the appropriate fractions provided
.alpha.-cyano-1-carboxycyclopentaneacetic acid diethyl ester as a clear
colorless viscous liquid (13 g, 66%).
The latter compound (13 g, 51 mmol) was mixed with 6N aqueous HCl (60 ml)
at 0.degree.. After dissolution, the reaction mixture was heated in a oil
barb at 120.degree. for 24 h. After this time water was removed from the
mixture using a dry ice rotory evaporator. The resulting white solid was
dried under high vacuum for 18 h. The dried material was dissolved in a
mixture of dioxane (50 ml) and 3N aqueous NaOH (52 ml). A solution of
di(tertiarybutyl) dicarbonate (14.6 g, 67 mmol) in dioxane (25 ml) was
added to the solution. The mixture was stirred at room temperature for 16
h. Additional 3N aqueous NaOH was added at intervals insuring a pH of
about 10. The mixture was diluted with water (500 ml) and extracted
(2.times.) with Et.sub.2 O (200 ml). The aqueous phase was rendered acidic
(pH=3) with solid citric acid and extracted (2.times.) with ethyl acetate
(300 ml). The combined ethyl acetate extracts were washed with water
(3.times.) and brine. Drying, filtering and concentration of the extract
afforded Boc-Asp(cyPn)-OH as a white solid (14 g, 96%).
To a solution of the latter compound (7.2 g, 25 mmol) in dry DMF (50 ml)
was added K.sub.2 CO.sub.3 (7.6 g, 55 mmol) and benzyl bromide (6.6 ml, 55
mmol). The reaction mixture was stirred at room temperature for about 7 h.
Thereafter, the reaction mixture was poured into a mixture of water (500
ml) and ethyl acetate (350 ml). The organic phase was washed with water
(2.times.) and brine. Drying, filtering and concentration of the extract
provided a pale yellow viscous liquid. This material was flash
chromatographed through a 5.times.20 cm column of silica gel, eluting with
hexane-ethyl acetate (12:1). Concentration of the appropriate fractions
provided the dibenzyl derivative of Boc-Asp-(cyPn)-OH as a low melting
white solid (11 g, 94%). The dibenzyl product was dissolved in TKF (100
ml) and an aqueous solution of LiOH (23.5 ml, 1N) was added. After 4 h,
the reaction mixture was poured into water and extracted (3.times.) with
Et.sub.2 O. The aqueous phase was rendered acidic with 10% aqueous citric
acid and extracted (2.times.) with ethyl acetate. The ethyl acetate layers
were combined, dried (MgSO.sub.4), filtered and concentrated to provide
Boc-Asp(cyPn)(OBzl)-OH as a clear color less gum (7.3 g, 82%).
EXAMPLE 5
General Procedure for the Solid Phase Preparation of Peptides of Formula 1
A modified version of the solid phase method of R. B. Merrifield, J. Am.
Chem. Soc., 85, 2149 (1963) was used to prepare the peptides, preferably
using a BHA-photoresin such as
›4-(2-chloropropionyl)phenoxy!acetamidomethyl-copoly(styrene-1%
divinylbenzene) resin, see D. Bellof and M. Mutter, Chemia, 39, 317
(1985). Protection of free carboxy groups and hydroxy groups was provided
by the Bzl protective group. Typically, a Boc-amino acid, representing the
C-terminal unit of the desired peptide, e.g. Boc-Leu-OH, was linked to the
above noted BHA-photoresin by the potassium fluoride method of K. Horiki
et al., Chem. Lea., 165 (1978), using 9 molar equivalents of KF and 3.6
molar equivalents of Boc-Leu-OH., for example, in DMF at 70.degree. C. for
24 h to give
›4-{2-(Boc-leucine)propionyl}phenoxy!acetamidomethyl-copoly(styrene-1%
divinylbenzene) resin. The dried amino acid-solid support typically showed
a leucine content of 0.6 to 0.8 mmol/g for the product, as determined by
deprotection of an aliquot, followed by picric acid titration, B. F.
Gisin, Anal. Chim. Acta, 58, 248 (1972). The latter amino acid-solid
support was used to build up the required sequence of units (i.e. amino
acid residues, derived amino acid residues) of the desired peptide by
solid phase methodology. Two molar equivalents (per mole of the amino
acid-solid support) of the appropriate amino acid residues were coupled
serially with the solid support system using BOP (2 molar equivalents), or
BOP (2 molar equivalents)/HOBt (1 molar equivalent), in the presence of
N-methylmorpholine (6 molar equivalents) in dry DMF. Completion of
coupling was verified by a negative ninhydrin test, E. Kaiser et al., Anal
Biochem., 34, 595 (1979). Double coupling was used when necessary.
Cleavage of the protected peptide from the solid support was accomplished
by irradiation at 330 nm in EtOH/DMF (1:4) at 0.degree. under an argon
atmosphere for 6 to 18 h. Protective groups (Bzl), if present, were
removed from the cleavage product by hydrogenolysis over 5% or 10% Pd/C or
20% Pd(OH).sub.2 /C by standard procedures (cf. example 1). Purification
of the final product was performed by reversed-phase HPLC to better than
95% homogeneity using 0.06% aqueous TFA/acetonitrile gradients.
More specifically exemplified, the protected peptide, PhCH:CH.sub.2
CO-N-Me-Val-Ile--NHCH(2-oxononyl)-CO-Asp(OBzl)-Leu-OH was assembled by the
preceding procedure on a BHA photoresin using BOP/HOBt as the coupling
agent and the intermediate of example 1, followed by cleavage of the
resulting protected peptide resin by photolysis under argon at -5.degree.
for 6 h. DMF:EtOH(4:1) was used as the photolysis medium. Deprotection of
the cleavage product was effected by hydrogenolysis using 5% Pd/C as
catalyst. Purification of the product was done by HPLC, the product being
dissolved in 0.1N aqueous NH.sub.4 H solution and the solution adjusted to
pH.sub.6 with 0.1N aqueous AcOH. Whatman Partisil.RTM. 100DS-3 C-18 column
(2.2.times.50 cm.sup.2), 10 micron particle size, was used. Elution was
done with a gradient of acetonitrile and 0.06% aqueous TFA. Pure fractions
(determined by analytical HPLC) were pooled and lyophilized to give
PhCH.sub.2 CH.sub.2 CO-N-Me-Val-Ile-NHCH(.sub.2 -oxononyl)-CO-Asp-Leu-OH.
MS: 824 (M+Na).sup.+.
In the same manner but replacing the intermediate of example 1 with the
intermediate of example 2, PhCH.sub.2 CH.sub.2
CO-N-Me-Val-Ile-NHCH(2-cyclopentyl-2-oxoethyl)-CO-Asp-Leu-OH was obtained.
MS: 773 (M +H).sup.+.
The above procedure was used to prepare other peptides of formula 1.
Commercially available Boc-amino acids were used. Unnatural amino acids
were used in their Boc protected form; they were either commercially
available, readily prepared from commercially available corresponding
amino acids by reaction with di-tertiary-butyl carbonate, or prepared by
standard methods.
EXAMPLE 6
Inhibition of Herpes Simplex Virus (HSV, type 1) Ribonucleotide Reductase
a) Preparation of Enzyme
HSV-1 ribonucleotide reductase (partially purified) was obtained from
quiescent BHK-21/C13 cells infected with strain F HSV-1 virus at 10 plaque
forming units/cell as described by E. A. Cohen et al., J. Gen. Virol., 66,
733 (1985).
b) Assay and Results for Exemplified Peptides
The procedure described by P. Gaudreau et al., J. Biol, Chem., 262, 12413
(1987), was employed. Results obtained for exemplified peptides of formula
1 are listed below. The assay result for each peptide is expressed as the
concentration of the peptide producing 50% of the maximal inhibition
(IC.sub.50) of enzyme activity. The number of units of the enzyme
preparation used in each assay was constant, based on the specific
activity of the enzyme preparation. The results are relative to the
activity obtained in control experiments without peptide and represent the
mean of four assays that varied less than 10% with each other.
______________________________________
PEPTIDE IC.sub.50 (.mu.M)
______________________________________
PhCH.sub.2 CH.sub.2 CO--N--Me--Val--Ile--NHCH(2-
0.42
oxononyl)-CO--Asp--Leu--OH
PhCH.sub.2 CH.sub.2 CO--N--Me--Val--Ile--NHCH(2-
0.18
cyclopentyl-2-oxoethyl)-CO--Asp--Leu--OH
PhCH.sub.2 CH.sub.2 CO--N--Me--Val--Ile--NHCH(2-
6.3
oxotridecyl)-CO--Asp--Leu--NH.sub.2
2-Ethylbutanoyl-Ile--NHCH(2-oxotridecyl)-
8.5
CO--Asp--Leu--OH
PhCH.sub.2 CH.sub.2 CO--N--Me--Val--Ile--NHCH(2-
1.3
oxopropyl)-CO--Asp--Leu--OH
2-Ethylbutanoyl-Ile--NHCH(2-oxononyl)-
24
CO--Asp--Leu--OH
2-Ethylbutanoyl-Tbg--NHCH(2-oxoheptyl)-
7.5
CO--Asp--Leu--OH
2-Ethylbutanoyl-Tbg--NHCH(2-oxononyl)-
4.5
CO--Asp--Leu--OH
2-Ethylbutanoyl-Tbg--NHCH(2-oxononyl)-
1.2
CO--NHCH›C(CH.sub.3).sub.2 COOH!--CO--Leu--OH
2-Ethylbutanoyl-Tbg--NHCH(2-cyclopentyl-2-oxoethyl)-
23
CO--Asp--NHCH.sub.2 CH.sub.2 C(CH.sub.3).sub.3
______________________________________
Other examples of the peptides of this invention are:
2-Biphenylcarbonyl-Val-Ile-(N-Me)-CH›4(R)-methyl-2-oxooctyl!-CO-Asp-Leu-OH
Octanoyl-N-Me-Val-NHCH(3-cyclohexyl-2-oxopropyl)-CO-NHCH-›CH(CH.sub.3)COOH!
-CO-NHCH›CH.sub.2 CH(CH.sub.3).sub.2 !-5-1H-tetrazole.sup.1
(3,4-Dihydroxy-Ph)CH.sub.2 CH.sub.2
CO-N-Me-Val-Ile-NHCH(2-oxo-5-phenylpentyl)-CO-Asp-leucinol
PhCH.sub.2 CH.sub.2
CO-N-Me-Val-Ile-NHCH(2-oxodecyl)-CO-Asp.PSI.›CSNH!-Leu-OH
PhCH.sub.2 CH.sub.2 CO-Ile-N-Me-CH(2-oxononyl)-CO-Asp-Leu-OH
Boc-N-Et-Val-Thr-NHCH(6-methyl-2-oxoheptyl)-CO-Asp-Leu-NHOH.sup.2
DAT-Ile-NHCH(2-oxo-5-phenylpentyl)-CO-Asp-Leu-N(CH.sub.3)OH.sup.2
PhCH.sub.2 CH, CO-N-Me-Val-Ile-NHCH(2-oxoundecyl)-CO-Asp-Leu-OH
PhCH.sub.2 CH.sub.2 CO-N-Me-Val-Ile-NHCH(2-oxotridecyl)-CO-Asp-Leu-OH
4-Methylpentanoyl-N-Me-Val-Ile-NHCH(2-oxotridecyl)-CO-Asp-Leu-OH
4-Methylpentanoyl-Ile-NHCH(2-oxopropyl)-CO-Asp-Leu-OH
4-Methylpentanoyl-Ile-N(CH.sub.3)CH(2-oxononyl)-CO-Asp-Leu-OH
PhCH.sub.2 CH.sub.2 CO-Tbg-NHCH(2-oxononyl)-CO-NHCH›C(C.sub.2
H.sub.5).sub.2 COOH!-NHCH.sub.2 CH.sub.2 CH(CH.sub.3).sub.2
2-Ethylbutanoyl-Tbg-NHCH(2-cyclohexyl-2-oxoethyl)-CO-Asp(cyBu)-Leu-OH
2-Ethylbutanoyl-Ile-NHCH(2-oxononyl)-CO-Asp(cyPn)-Leu-OH
(1) The tetrazole residue or unit for this peptide was derived from
Boc-Leu-NH.sub.2 in the following manner: Boc-Leu-NH.sub.2, was convened
to the corresponding nitrile derivative by treatment with
p-toluenesulfonyl chloride in CH.sub.2 Cl.sub.2 in the presence of excess
pyridine and a catalytic amount of 4-dimethylaminopyridine (Fieser and
Fieser, "Reagents for Organic Synthesis", John Wiley and Sons, Inc., New
York, N.Y., USA, 1967, vol 1, p 1183). The nitrile derivative then was
mixed with tributyl tin azide, J. G. A. Luijten et al., Rec. Trav., 81,
202 (1962), giving a tetrazole tin derivative (cf. K. Sisido et al.,
Journal of Organometallic Chemistry, 33, 337 (1971). The latter was
treated with HCl gas in Et.sub.2 O to afford the desired tetrazole residue
as a hydrochloride salt which was used as such for the coupling with an
activated amino acid.
(2) Terminal hydroxamic acids and terminal N-(lower alkyl)hyroxamic acids
are obtained by coupling the corresponding protected C-terminal acid with
hydroxylamine hydrochloride or N-(lower alkyl)hydroxylamine hydrochloride,
respectively, using BOP/DIPEA in CH.sub.2 Cl.sub.2, followed by the
removal of any protecting groups.
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